• Geomechanics and Engineering
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• 제33권2호
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• pp.203-209
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• 2023

One major advantage of ground penetrating radar (GPR) over other field test methods is its ability to obtain subsurface images of roads in an efficient and non-intrusive manner. Not only can the strata of pavement structure be retrieved from the GPR scan images, but also various irregularities, such as cracks and internal cavities. This article introduces a deep learning-based approach, focusing on detecting subsurface cracks by recognizing their distinctive hyperbolic signatures in the GPR scan images. Given the limited road sections that contain target features, two data augmentation methods, i.e., feature insertion and generation, are implemented, resulting in 9,174 GPR scan images. One of the most popular real-time object detection models, You Only Learn One Representation (YOLOR), is trained for detecting the target features for two types of subsurface cracks: bottom cracks and full cracks from the GPR scan images. The former represents partial cracks initiated from the bottom of the asphalt layer or base layers, while the latter includes extended cracks that penetrate these layers. Our experiments show the test average precisions of 0.769, 0.803 and 0.735 for all cracks, bottom cracks, and full cracks, respectively. This demonstrates the practicality of deep learning-based methods in detecting subsurface cracks from GPR scan images.

• 대한치과보철학회지
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• 제55권4호
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• pp.372-380
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• 2017

목적: 본 연구는 보철물의 적합도를 계측하는 두 가지의 측정방법을 평가하기 위해 지르코니아로 전부도재관을 제작하고 replica technique과 triple-scan protocol을 이용하여 전부도재관의 변연 및 내면 적합도를 비교 연구하고자 하였다. 재료 및 방법: 타이타늄의 지대치 모형을 제작하여 20개의 지르코니아 전부도재관을 제작하였다. 제작된 지르코니아 전부도재관 10개는 replica technique을 이용해 복제하고 복제된 시편을 협설, 근원심으로 절단하여 변연 및 내면 적합도를 측정하였고, 다른 10개의 전부도재관은 triple-scan protocol을 이용하여 협설과 근원심으로 단면을 형성하고 변연 및 내면 적합도를 계측하여 통계 분석하였다 (${\alpha}=.05$). 결과: 변연과 내면 적합도는 replica technique $49.86{\pm}29.69{\mu}m$, triple-scan protocol $75.35{\pm}64.73{\mu}m$로 유의한 차이가 있었고 (P < .001), 내면 적합도만을 측정한 결과 각각 $58.38{\pm}31.77{\mu}m$, $64.00{\pm}46.43{\mu}m$로 유의한 차이가 없었다 (P > .343). 결론: Replica technique과 triple-scan protocol을 이용하여 전부도재관의 변연 및 내면 적합도를 비교 측정한 결과 triple-scan protocol에서의 변연 적합도가 크게 측정되었고, 내면 적합도만 비교해 본 결과 통계적인 유의한 차이가 없었다.

• 한국지능시스템학회논문지
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• 제21권5호
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• pp.555-563
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• 2011

영상의 왜곡보정은 영상 좌표계(이미지)와 전역 좌표계(대상체)의 상관관계를 규정하는 것이다. 기존의 왜곡영상에 대한 보정은 카메라의 광학적 특성을 모델링하여 영상 좌표계와 전역 좌표계의 물리적 관계를 찾는 방식이 주를 이루고 있다. 본 논문에서는 성능 지수기반 다항식 모델을 이용하여 왜곡영상의 보정을 시도하였다. 성능지수기반 다항식 모델은 영상 좌표계와 전역 좌표계 사이의 상관관계를 다항식으로 가정한 후, 이미지와 대상체의 좌표 데이터와 성능지수를 이용하여 다항식 모델의 계수와 차수를 결정하는 방식이다. 제안한 성능지수기반 다항식 모델을 이용하여 기존의 왜곡영상을 보정방식이 가진 과대적합 문제와 같은 한계를 극복하고자 한다. 제안한 방법을 레이저 스캔 카메라로 획득한 2차원 영상에 적용하여 모델의 유효성을 검증하였다.

• The Journal of Advanced Prosthodontics
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• 제12권2호
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• pp.49-54
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• 2020

PURPOSE. The purpose of this study was to compare the performance of Accura to that of the T-scan for indicating occlusal contacts. MATERIALS AND METHODS. Twenty-four subjects were selected. Their maxillary dental casts were scanned with a model scanner. The Stereolithography files of the casts were positioned to align with the occlusal plane. Occlusal surfaces of every tooth were divided into three to six anatomic regions. T-scan and Accura recordings were made during two masticatory cycles. The T-scan and Accura images were captured at the maximum bite force and overlapped to the cast. Photographs of interocclusal records were used as the reference during overlap. The occlusal contacts were counted to compare the T-scan and Accura. McNemar's test was used for statistical significance and the corresponding P-values were calculated from a chi-square distribution with one degree of freedom. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Accura were calculated relative to the T-scan values as a control. RESULTS. No statistical differences (P>.05) were found between the T-scan and Accura methods. The accuracy of Accura was 75.8%, sensitivity was 82.1%, specificity was 60.1%, PPV was 82.9%, and NPV was 60.1%. CONCLUSION. Accura could be another possible option as a computerized occlusal analysis system for indicating occlusal contacts at maximum intercuspation.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.1
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• pp.167-172
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• 2006

High-yield Pinus radiate kraft pulps with various Kappa number were produced from flow-through laboratory pulping. The samples were prepared and scanned using a rapid scan photoacoustic Fourier transform infrared (PAS-FTIR) spectrometer. A partial-least-squares (PLS) model was established based on the spectral data collected at different mirror velocities. The model was used to predict the Kappa number of the pulps and its robustness was statistically evaluated. The outcomes indicate that the PLS model can be used to predict the Kappa number of Pinus radiata kraft pulps with a high degree of accuracy provided that the moving mirror velocity is ${\leq}\;0.5cm/s$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.251-252
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• 2006

• Spatial Information Research
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• 제13권2호
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• pp.157-166
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• 2005

본 연구에서는 항공레이저측량(LiDAR; Light Detection And Ranging)을 이용한 지상지형자료(DEM, DSM DTM 등)와 단빔 음향측심기(SBES; Single Beam Echo Sounder), 측면음향주사기(SSS; Side Scan Sonar)를 이용한 하저 지형자료의 통합방안을 모색하고, LiDAR 데이터와 SSS/SBES 데이터를 통합하고 지형의 2차원 및 3차원 그래픽 표현, 수량계산 등의 기능을 갖는 소프트웨어를 개발하였다. 개발한 소프트웨어의 정확도 비교는 상용 소프트웨어인 Surfer를 이용하였다.

• 한국건설관리학회논문집
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• 제25권2호
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• pp.69-80
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• 2024

Currently rebar spacing inspection is carried out by human inspectors who heavily rely on their individual experience, lacking a guarantee of objectivity and accuracy in the inspection process. In addition, if incorrectly placed rebars are identified, the inspector need to correct them. Recently, laser scanning and AR technologies have been widely used because of their merits of measurement accuracy and visualization. This study proposes a technology for rebar spacing inspection and fixing by combining laser scanning and AR technology. First, scan data acquisition of rebar layers is performed and the raw scan data is processed. Second, AR-based visualization and fixing are performed by comparing the design model with the model generated from the scan data. To verify the developed technique, performance comparison test is conducted by comparing with existing drawing-based method in terms of inspection time, error detection rate, cognitive load, and situational awareness ability. It is found from the result of the experiment that the AR-based rebar inspection and fixing technology is faster than the drawing-based method, but there was no significant difference between the two groups in error identification rate, cognitive load, and situational awareness ability. Based on the experimental results, the proposed AR-based rebar spacing inspection and fixing technology is expected to be highly useful throughout the construction industry.

• 천문학회지
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• 제25권1호
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• pp.23-46
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• 1992

The electrical, mechanical and optical capabilities have been tested of the microdensitometer PDS 1010GMS at the Korea Astronomy Observatory. The highest stage of scan speed 255 csu (conventional speed unit) is measured to be 47 mm/s. At this speed the position is displaced by $4{\mu}m$ to the direction of scanning and the density is underestimated by $0.4{\sim}0.7D$. Standard deviation in the measured density is proportional to $A^{-0.46}$, where A is the area of scan aperture. The accuracy of position repeatability is ${\pm}1{\mu}m$, and that of density repeatability is ${\pm}(0.003{\sim}0.03)D$. Callier coefficient is determined to be 1.37; the semispecular density is directly proportional to the diffuse density up to 3.5D. Because the logarithmic amplifier has a finite response time, the densities measured at high scan speeds are underestimated to the degree that speeds higher than 200 csu are inadequate for making an accurate astronomical photometry. After power is on, an about 5 hour period of warming is required to stabilize the system electrically and mechanically as well. On the basis of this performance test, we have determined the followings as the optimum scan parameters for the astronomical photometry: For the scan aperture $10\;\sim\;20{\mu}m$ is optimal, and for the scan speed. $20\;{\sim}\;50$ csu is appropriate. These parameter values are chosen in such a way that they may keep the density repeatability within ${\pm}0.01D$, the position displacement under $1{\mu}m$, and the density underestimation below 0.1D even in high density regions.

• 대한의용생체공학회:의공학회지
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• 제39권3호
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• pp.116-123
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• 2018

This study is a model experimental study using a phantom to propose an optimized brain CT scan protocol that can reduce the radiation dose of a patient and remain quality of image. We investigate the CT scan parameters of brain CT in clinical medical institutions and to measure the important parameters that determine the quality of CT images. We used 52 multislice spiral CT (SOMATOM Definition AS+, Siemens Healthcare, Germany). The scan parameters were tube voltage (kVp), tube current (mAs), scan time, slice thickness, pitch, and scan field of view (SFOV) directly related to the patient's exposure dose. The CT dose indicators were CTDIvol and DLP. The CT images were obtained while increasing the imaging conditions constantly from the phantom limit value (Q1) to the maximum value (Q4) for AAPM CT performance evaluation. And statistics analyzed with Pearson's correlation coefficients. The result of tube voltage that the increase in tube voltage proportionally increases the variation range of the CT number. And similar results were obtained in the qualitative evaluation of the CT image compared to the tube voltage of 120 kVp, which was applied clinically at 100 kVp. Also, the scan conditions were appropriate in the tube current range of 250 mAs to 350 mAs when the tube voltage was 100 kVp. Therefore, by applying the proposed brain CT scanning parameters can be reduced the radiation dose of the patient while maintaining quality of image.